Wales face the Group B leaders on 28 March with Roberts admitting it is "going to be tight" whether Chester is fit to play.

"We'll have to see how he gets on over the next few weeks," he added.

Chester has played every minute of every game in the qualifying campaign up to now, which has seen Chris Coleman's team pick up eight points in an unbeaten start.

They are a point behind their next opponents, who have maximum points from three matches.

Roberts added: "He's played an integral part of what we've achieved so far, but if he's not available then that will give somebody else an opportunity and that player will have to be ready to step out on the pitch and perform."